Vietnam-made game Flappy Bird is today's number one app in the iOS App Store in over 100 countries. It already has more than 50 million downloads and it even beat Facebook's Paper app. Anh-Minh Do of Tech in Asia explains the popularity of the game:

It’s so hard that it’s ridiculously frustrating, annoying, and somehow existentially hilarious. It’s so hard it’s funny. In this way, Flappy Bird is punishing. If you take a gander at the reviews on the App Store, you’ll immediately see how much people love to hate it. And this is probably the single biggest reason for its success. People love to torture themselves, and they love to share it. The difficulty of the game is engineered for virality.